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Sikaflex 221 vs. 522

The differences in uses and application of Sikaflex 221and Sikaflex 522

Difficulty: Easy


Both 221 and 522 (previously known as 512) are non-corrosive adhesive sealants bond well to a wide variety of substrates with permanent elasticity. They are low odour and resistant to aging, weathering, and UV. They both can be sanded and overpainted.


So, What’s the Difference?

The main difference is that 522 was specifically made for caravans, motorhomes, and trailers. While 221 is one part polyurethane, 522 is the hybrid version and has extra resistance to UV breakdown. It was designed to bond to metal primers, paint coatings, vehicle components and plastic. 522 is fast curing and can be used for interior and exterior jobs while 221 is more suited to interior and simple bonding applications.


This means 522 is especially suited to heavy duty jobs such as repairing skylights, solar panels and satellite dishes, whereas you may find 221 more suitable for jobs such as sealing around windows.


Another difference is that Sikaflex 221 comes in white, black, brown, and grey whilst 522 only comes in white. However, if you have a job more suited for 522, it can be sanded and overpainted.



Whilst they have different strengths and uses, they are applied similarly. It is important before application that you take necassary safety measures; wear gloves and safety goggles and apply in a well-ventilated area.


To prepare your surface, clean with a multi-purpose cleaner and a microfibre cloth. Dry with a drying cloth.


Screw the cap onto the cartridge of the sealant and cut the tip. Place the cartridge inside a caulking gun and apply to your designated area.


For a specific tutorial on how to reseal trims on motorhomes and caravans, click here.


After allowing the sealant to dry, you can then sand or overpaint.


Products Used In This Tutorial

Sikaflex 221

Sikaflex 221 White 310ml cartridge


Sikaflex 522

Sikaflex 522 Caravan & Motorhome Adhesive Sealer White, 300ml


Microfibre Cloth

Farecla Finishing Cloth (Pack of 3)


3M Microfibre Detailing Cloth


Multi-Purpose Cleaner

Meguiar's Heavy Duty Multi-Purpose Cleaner, 709ml


Drying Cloth

Meguiars Water Magnet Microfibre Drying Towel


Sealant Gun

These are avilable from hardware shops or online.